prin- +

1. A male member of a royal family other than the monarch, especially a son of the monarch.
2. A man who is a ruler of a principality.
3. A hereditary male ruler; a king.
4. A nobleman of varying status or rank.
5. An outstanding man, especially in a particular group or class.

1. Relating to, belonging to, or suitable for a prince.
2. Of or relating to a prince; royal.
3. Generous as an amount of money, or requiring the expenditure of large sums of money: "They donated a princely sum to the charity."

A female member of a royal family other than the queen (especially the daughter of a sovereign).

1. A chief or head.
2. The head or director of a school or; especially, in England, a college.
3. A person who takes a leading part in any activity, as a play; a chief actor or performer.
4. The first player of a division of instruments in an orchestra (except the leader of the first violins).
5. Something of primary or chief importance.

Learn how to distinguish between principal and principle.

1. A territory ruled by a prince or princess.
2. The position or jurisdiction of a prince.

1. For the most part, chiefly.
2. Above all; especially.
3. Almost entirely; mainly.

1. An accepted or professed rule of action or conduct: "She was a person of good moral principles."
2. A fundamental, primary, or general law or truth from which others are derived; such as, the principles of physics.
3. A fundamental doctrine or tenet.
4. Principles, a personal or specific basis of conduct or management: "He was known as someone who always stirved to adhere to his principles."
5. Guiding sense of the requirements and obligations of right conduct; a person of principle.
6. A rule or law exemplified in natural phenomena, the construction or operation of a machine, the working of a system, or the like.

Learn how to distinguish between principle and principal.

Based on, marked by, or manifesting principle: a principled decision; a highly principled person.

Principal-Principle Words, Quiz #1.

Principal-Principle Words, Quiz #2.

Lacking principles or moral scruples; unscrupulous: unprincipled behavior.